The involuntary forcible expulsion of stomach contents through the mouth. Vomiting can be preceded by nausea, sweating, excessive salivation, pallor, and a slowed heart rate.
It arises when the vomiting centre in the brainstem is activated by signals from one of three places within the body: the digestive tract; the balancing mechanism of the inner ear; or the brain, either due to emotions or thoughts or via the part of the brain that responds to poisons in the body.
The vomiting centre sends messages to both the diaphragm, which presses down on the stomach, and the abdominal wall, which presses inwards; the combined effect of these actions is to expel the stomach contents upwards through the oesophagus.
Vomiting can be the result of over indulgence in alcohol or food. It is also a frequent side effect of a number of drugs, and it can follow after general anaesthesia.
Vomiting is also widespread in gastrointestinal disorders such as peptic ulcer, gastroenteritis, acute appendicitis, and food poisoning. Less frequently, it is due to intestinal obstruction (for example, due to pyloric stenosis or intussusception) or a tumour of the digestive tract. It can also be due to inflammation of associated digestive-tract organs.
Other possible causes of vomiting are pressure within the skull, migraine, conditions that affect the ears balancing mechanism, and hormonal disorders.
Vomiting can be a symptom of ketoacidosis in badly controlled diabetes mellitus. It can also be a symptom of an emotional problem or be part of disorders such as bulimia or anorexia nervosa.
Constant vomiting needs medical investigation. Treatment depends on the cause.